This invention relates to rotary power transmissions. More specifically, this invention relates to a rotary power transmission for providing a rotational output having a speed which is continuously variable throughout a prescribed speed range without varying the speed of driving input, and which is capable of providing a reversible rotational output in response to a non-reversing rotational input.
A wide variety of mechanical rotational power transmissions are available throughout the art, and these transmissions typically comprise a plurality of gears meshed together to convert a rotational input to a rotational output of the desired speed. In one common form, these rotary power transmissions include a so-called planetary gear train including a sun gear, a ring gear, and a cage having planet gears meshed between the sun and ring gears. The planetary gear train responds to a rotational input to provide an appropriate speed-adjusted rotational output. Of course, variation in the speed of the driving input correspondingly varies the rotational speed of the driven output.
In many applications of rotary power transmissions, it is highly desirable to reverse the rotational direction of the driven output during at least some conditions of operation. In the prior art, reversal of the output has been achieved by disengaging members of the gear train in order to disconnect the driving input from the driven output, and then by coupling an idler gear into the gear train to reverse the rotational direction of the driven gears. However, this engaging and disengaging of gear train members results in substantial wear of the various gear train components. Moreover, this arrangement requires the use of additional gears and a clutch device for controlling engagement and disengagement of the gear train members, and these additional components are also subject to wear and resulting periodic maintenance.
The present invention overcomes the problems and disadvantages of the prior art by providing an improved rotary power transmission including a plurality of gear train elements and associated control mechanisms arranged for providing a rotational output of continuously variable speed without varying the speed of a rotational input and which can be adapted for reversible operation in response to a non-reversing rotational input without requiring engagement and disengagement of gear train elements.